The purpose of this competitive renewal application is to request continued National Service Research Award support for four pediatric hematology-oncology fellows annually (two second-year and two third-year) in the Department of Pediatrics at The University of Texas Southwestern Medical Center at Dallas (UT Southwestern). These awards will be used to support research training of young pediatricians who have completed a clinical fellowship year devoted to patient diagnosis and management and exposure to research methods. The pediatric hematology-oncology fellowship program at UT Southwestern was developed in the mid-1980's with the broad aim of training physicians committed to full-time careers in the academic arena, a vital need in view of the continued national shortage of clinical and laboratory scholars in pediatric hematology-oncology. The continued success of this fellowship training program at UT Southwestern is assured, given: (1) a large, diverse, and readily accessible patient population, (2) a track record of clinical and laboratory investigative excellence in areas such as cancer therapeutics, molecular oncology, cancer survivorship, sickle cell disease, hemorrhagic and thrombotic disorders, oncologic supportive care, and cancer genetics, (3) well functioning collaborations with and commitment from outstanding basic science investigators, and (4) existing infrastructure and major new institutional initiatives on patient-oriented research. These features combined provide an excellent environment for cutting-edge research training of fellows supported by the requested stipends. Current and former pediatric hematology-oncology trainees have worked under the preceptorship of investigators in diverse research areas. Since the initial award in 1990, thirty-one trainees have received institutional NRSA support and most have been successful as clinical or laboratory investigators or continue as fellows. The stimulating intellectual involvement in the Division of Pediatric Hematology-Oncology and its multiple collaborating laboratories and clinical research domains at UT Southwestern will continue to provide the rich milieu necessary for trainees to become independent investigators.